Hydrogenation process



Jan. 26, 1960 w. G. scHLlNGER HYDROGENATION PRocEss Filed April 6, 1955 lll ` tungsten-sulfide.

United States Patent p HYnRoeENA'rIoN PRocEss Warren G. Schlinger, Altadena, Calif., assignor t0 Texaco Inc., a corporation of Delaware Application April 6, 1955, Serial No. 499,669

12 Claims. ,(Cl. 208-212) This invention relates to the hydrogenation of petroleum hydrocarbons. More particularly, it relates to a process by which a motor fuel fraction containing sulfur may be treated to produce a product `of reduced sulfur and improved quality.

The invention contemplates the mild hydrogenation of gasoline, naphtha, diesel oil, jet engine oil or other hydrocarbon mixture characterized as an internal combustion engine fuel or more succinctly, motor fuel. Mild hydrogenation of the foregoing motor fuel stocks may be variously Vemployed to improve the quality of the stock by reducing the sulfur content and improving the storage stability, engine cleanliness characteristics, color or odor of the treated stock.

In the invention, a motor fuel stock containing sulfur is contacted with a hydrogen-containing gas under mild hydrogenating conditions in the presence of a sulfuractive catalyst, followed by a primary fractional distillation at substantially the pressure of the hydrogenation zone and in the presenceof the hydrogen-containing gas supplied to said`zone. In this primary fractional distillation, a separation is effected between desired motor fuel components and a fraction containing undesirable high boiling components. After the primary fractionation, hydrogen-rich gas is separated from a liquid fraction at substantially the pressure of the foregoing hydrogenation and primary distillation steps. This liquid fraction is then redistilled to adjust the initial boiling point or volatility Vof the motor fuel fraction by removing a relatively small amount of low boiling components. This redistillation is conducted at conditions ordinarily used for the separation of a relatively small amount of low boiling components and may be at a pressure substantially lower than the foregoing steps.V The high boiling fraction from the primary distillation may also be redistilled in a separate fractional distillation and may be at somewhat lower pressure than the primary distillation pressure to recover as distillate any components boiling within the boiling range of the desired motor fuel fraction` The recovered constituents may be blended into the motor fuel fraction.

Mild hydrogenation is characterized as the reaction of hydrogen with a hydrocarbon fraction or component thereof under conditions such that substantial cracking or the formation of lower boiling components is avoided. The process is commonly carried out at temperatures from 500 to 900 F. and at pressures from atmospheric to 1500 p.s.i.g. Liquid hourly space velocities from 0.5 to l5 volumes of oil per hour per volume of catalyst are employed. A hydrogen-containing gas is supplied at a rate of about 200 to 20,000 cubic feet per barrel of oil charged and about 20jto 1000 cubic feet of hydrogen per barrel of oil is consumed. Sulfur-active catalysts are used such as molybdenum-oxide-alumina, chromia-alurnina, cobalt-molybdate, molydbenum-suliide and nickel- Supported noble metal catalysts have been foundruseful in some applications.

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for the redistillation steps may be varied considerably for particular commercial installations.

ln the operation of the process of this invention, rmild hydrogenation is carried out at a pressure of at least 200 p.s.i.g. preferably about 500 p.s.i.g. and the primary fractional distillation is carried out at a pressure above 200 p.s.i.g. preferably at substantially the hydrogenation reaction pressure.

The usual means of controlling sulfur, gum, and stability of motor fuels is by acid treating. Although itis well-known that motor fuel stocks can be, effectively treated by hydrogenation, the operating costs and investment required for hydrogenation have formerly made it unattractive economically. However, the recent availability of large quantities of hydrogen from the catalytic reforming of gasolines has improved the relative economics of hydrogenation. The present invention further enhances the attractiveness of this process by yielding a product of unexpectedly high quality accompanied by improved efficiency in the utilization of fuel and power.

The method of the present invention has many advantages over those previously employed for the treatment of motor fuels. One advantage is that the formation of gum precursors during distillation is avoided by conducting thedistillation under a high hydrogen partial pressure.

Another advantage is that the heat content of the hydrogenation reaction may be employed to effect the primary distillation of a large portion of the products. Only a small amount of additional heat is required to strip desirable components from the residue fraction and to separate low boiling components from the motor gasoline fraction and, since the fractionation load is small in these cases, only relatively small and economical equipment is required.

A further advantage of this invention is that sulfur and gum-forming components are removed with virtually no loss in yield, whereas conventional treatment with sulfuric acid is accompanied by substantial yield losses.

Another advantage is that the process is capable of efficiently using by-product hydrogen from catalytic re'- forming which otherwise would be of low value as fuel. Other advantages will appear from the description and examples given below. l The accompanying drawing diagrammatically illustrates the process of my invention. Although the drawing illustrates one arrangement of apparatus in which the process of my invention may be practiced, it is not intended to limit the invention to the particular apparatus or material described. Y

Hydrogen or a hydrogen-containing gasis drawn from an external source, not shown, and is admitted to hydrogen inlet line 1. Thegasoline, naphtha, or other vhydrocarbon mixture to be treated is withdrawn from external storage, not shown, and is'admitted to the lfeed inlet line 2. The hydrogen and hydrocarbon feed vare4 com bined in line 3 and thenheated and vaporized in preheater 4. The preheater etlluent flows through transfer line 5 to the topof reactor 6 which contains asulfurresistant hydrogenation catalyst. The vcombined lnyilrr-V carbon and hydrogen in vapor form pass downwardly through the catalyst and then out through transfer line 7 to cooler 8. Suicient heat is removed in cooler 8 to completely desuperheat the reactor efliuent and to condense a portion of the hydrocarbon contained therein.

The mixture of liquid and vapor passes through transfer line 9 to degummer tower 10 elsewhere referred to herein asa primary fractional distillation means. Degummer tower 10 is a fractional-distillation means which employs the sensible heatof the charge to effect a preliminary separation between the desired product and a fraction containing the higher boiling polymers present in the reactor effluent. This separation is made in the presence of the hydrogen contained in the reactor efuent and at a pressure substantially that prevailing in the aforesaid reaction zone. The high boiling polymer fraction is discharged from ythe degummer tower 10,. through transfer line 11 and control valve 12.v The pressure in the system is reduced at control rvalve 12 and the high boiling polymer fraction flows to rerun tower 13.

The rerun tower 13 is a conventional low pressure fractional distillation means and is used to recover a relatively small amount of distillate boiling in the distillation range of the desired product which is incompletely separated from the high boiling fraction in degummer tower 10.A The heavy polymer discharged as a bottoms product from rerun tower 13 is removed through transfer line v14 to external tankage or disposal, not shown. Recovered' distillateY product from rerun tower 13v is discharged through transfer line 15 to external hydrotreated product storage, not shown.

Returning to degummer tower 10, vapors are removed overhead through line 16, passed through cooling and condensing means 17 and are discharged into separator 18. Gas from separator 18 isrich in hydrogen and may be removed from the system through transfer line 19 for other uses or is suitable as a source of hydrogen-rich gas for inclusion in the feed to hydrogen inlet line 1 by provision of suitable recycle and hydrogen sulfide removal means, not shown. A portion of the liquid from' separator 18 is returned as redux to degurnmer tower 10 through line 20. The remaining liquid in separator 18 is discharged through line 21 and control valve 22. Control valve 22 reduces the pressure of the separated liquid stream which then flows to stripping tower 23. Stripping tower 23 is a fractional distillation means operated to depropanize or debutanize the hydrogenated product as desired to produce a product of suitable vapor pressure. Gas from stripping tower 23 may be used as fuel or for other external uses and is discharged from the process through transfer line 24. Liquid product from the bottom of stripping tower 23 is finished hydrogenated product and is removed through line 25, combined with recovered product in line 15, and discharged to finished hydrogenated product storage, not shown.

The preheater outlet temperature is adjustedto obtain the desired degree of refining in the subsequent reaction zone. It may be found necessary to increase the preheater outlet temperature during the course of operation to compensate for any decline in catalyst activity.V A1- though any sulfur-resistant catalyst having hydrogenation I activity may be used in this process, molybdenum-oxidealumina or cobalt-molybdate catalysts are particularly suitable for this purpose. A molybdenum-oXide-alumina dehyd'ro-aromatization catalyst which has become spent for that purpose is entirely'satisfactory for the present mild hydrogenation process.

The invention will be further illustrated by the following examples. Y

Example I Heavy naphtha blends composed of heavyl catalytically cracked and heavy'thermally cracked naphthas are hydro'- 4 genated over a molybdenum-oxide-alumina catalyst at conditions and with the results following:

Run A Run B Temperature, F.:

Preheater Outlet 686 614 Average Reactor Temp 712 657 Deg'ummer eed 609 615 Degummer Overhead- 545 574 Pressures, p.s.i.g.:

Preheat-er Inlet 513 5l2 Degummer Outlet; 497 494 Liquid Hourly Space Velocity. 3.0 3.0 Hydrogen rate, cu. t./bbl 950 890 Tests on feed and products:

Degummed Degummed Feed Product Feed Product (caustic (caustic washed) washed) Gravity, API 43.0' 43. 3 42. 6 44.4 Lamp Sulfur. wt. percent 569 410 583 388 Bromine No 58 46 47 33 Gen. Motors Sludge No.1 170 33 170 24 Gum, ASTM, mg 49 4 32 4 1 Described in report Trends in Motor Fuels by H. R. Wolf, presented September 18, 1947, at the 45th Annual Meeting of the National Petroleum Association held at Atlantic City, NJ.

Example II A heavy naphtha having an ASTM gum of 28 milligrams and a distillation end point of 430 F. is catalytically hydrogenated at about 500 p.s.i.g., 700 F. and 1000 cubic feet per barrel of admixed hydrogen. The product from the hydrogenation zone has an ASTM gum of l0 to l5 milligrams and a distillation end point 445 F. However, by subjecting the 'effluent from the hydrogenation zone to fractional distillation at substantially the pressure of the hydrogenation zone land in the presence of the admixed hydrogen, a 430 F. end point product is obtained having an ASTM gum of 5 milligrams.

Example Ill A heavy naphtha feed containing .56 weight percent sulfur is hydrogenated with a highly active cobalt-molybdenum catalyst in the presence of about 1000 cubic feet per barrel of hydrogen at a pressure of 500 p.s.i.g., reactor temperatures at 540 F. inlet and 620 F. outlet, and at a space velocity of 3.0 volumes of oil per volume of catalyst to produce a product containing .39 weight percent sulfur.

Example IV In another example a molybdenum-oxide-alumina catalyst is used which has previously been used for dehydroaromatization until the dehydro-aromatization activity has been substantially reduced. The unused molybdenum-oxide-alumina catalyst, before used for dehydroaromatization, has a surface area of square meters pery gram.1 The catalyst employed in this example was used for dehydroaromatization until the surface area had been reduced to 55 square meters per gram at which time it had become spent for dehydro-aromatization.

A heavy naphtha feed containing .56 weight percent sulfur is hydrogenated using this spent molybdenumoxide-alumina dehydro-aromatization catalyst in the presence of about 1000 cubic feet per barrel of hydrogen at a pressure of 500 p.s.i.g., reactor temperatures of 720 F. inlet and 800 F. outlet and at a space velocity of 3.0 volumes of oil vperrvolume of catalyst to produce a product containing' .39w`eight percent sulfur.

Example I shows typical conditions of a preferred embodiment of'my invention. Example II sets forth specifically the improvement obtained by performing the primary fractional distillation at substantially the pres- 1Determined by nitrogen adsorption -using the method reported by BruanuenS., Emmett, P. H.. 4and Teller E., J. Am. chem. soc, so, soa-19 (193s).

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sure of the hydrogenation `zonei and in the presence of the hydrogen employed inthe saidhydrogenation zone. Example III shows typical conditions 'employed for the hydrogenation stepwhen-an active f cobalt-molybdenum catalyst is used: Example IV-sliows conditions under which a molybdenum-oiride-alumina dehydro-aromatization catalyst which has become spent forv that purpose is satisfactory for use in my Vhydrogenation process. U f

Obviously, many modifications and variations of the invention, as hereinbeforeVV set forth, may be made without departing from the spirit vand scope thereof, and only such limitations should be imposed as are indicated in theappended claims.

1. A methodof refining asulfur-containing hydrocarbon motor fuel fraction which comprises hydrogenating said fraction' with ar hydro gen-containing gas at al pressure above about 200 p.s.i.g. under conditions wherein at least a portion of the sulfur is converted to hydrogen sulfide, subjecting the hydrogenation product to a primary fractional distillation at substantially the pressure of the hydrogenation zone and in the presence of unreacted hydrogen-containing gas supplied to said hydrogenation zone to effect a separation between a fraction containing desired motor fuel components and a fraction containing undesirable high boiling components, separating hydro gen-containing gas from said fraction containing motor fuel components, and distilling said motor fuel fraction at lower pressure to remove components lower boiling than the desired motor fuel components.

2. A method according to claim 1 wherein the hydrogen-containing gas charged to the hydrogenation zone contains 500 to 5000 cubic feet of hydrogen per barrel of sulfur-containing motor fuel feed stock.

3. A method according to claim 1 wherein the hydrogenation zone is maintained at a pressure of 400 to 600 p.s.1.g.

4. A method according to claim l wherein said undesirable high boiling fraction is redistilled at a pressure lower than the primary fractional distillation pressure to remove as distillate a fraction boiling within the boiling range of the desired motor fuel fraction and said distillate is blended with said desired motor fuel fraction.

5. In the method of refining a sulfur-containing hydrocarbon motor fuel fraction by vapor phase mild hydrogenation in the presence of a hydrogen-containing gas at a pressure above about 200 p.s.i.g. under conditions wherein at least a portion of the sulfur is converted to hydrogen sulfide without substantial cracking of said hydrocarbon motor fuel fraction followed by fractional distillation to separate a fraction boiling within the distillation range of desired motor fuel components from a fraction containing undesirable components, the improvement which comprises initially distilling efiiuent from the mild hydrogenation zone at substantially the pressure of the hydrogenation zone and in the presence of unreacted hydrogen-containing gas supplied to said hydrogenation zone to effect a separation between a fraction containing desired motor fuel components and a fraction containing undesirable high boiling kcomponents wherein heat contained in said efiiuent supplies all the heat required for said fractional distillation.

6. A method of refining a sulfur-containing hydrocarbon motor fuel fraction which comprises passing said sulfur-containing motor fuel fraction in admixture with a hydrogen-containing gas into a hydrogenation zone containing a sulfur-resistant hydrogenation catalyst at a temperature of 500 to 850 F. and at a pressure from 200 to 1500 p.s.i.g. for a time sufiicient to convert at least a portion of the sulfur contained therein to hydrogen sulfide without substantial cracking of said hydro` carbon, subjecting the total effluent from the hydrogenation zone to a primary fractional distillation at substantially the pressure of the hydrogenation zone to effect a bon motor fuel fraction which comprises passing said separation between a fraction containing desired motor sulfur containing motor fuel fraction in admixture with a hydrogen-containing gas into a hydrogenation zone containing a sulfur-resistant hydrogenation catalyst at a temperature of 500 to 850 F. and at a pressure of 200 to 1000 p.s.i.g. for a time sufncient to convert at least a portion of the sulfur contained therein to hydrogen sulfide without substantial cracking of said hydrocarbon, cooling the efiiuent from the hydrogenation zone to effect partial condensation thereof and subjecting said effluent from the hydrogenation zone to a primary fractional distillation at substantially the pressure of the hydrogenation zone wherein heat contained in said efliuent supplies all the heat required for said fractional distillation whereby hydrogen, hydrogen sulfide, gaseous hydrocarbons and a major portion of the motor fuel fraction boiling within the distillation range of the desired product is separated as a distillation overhead fraction from a residue fraction containing heavy components boiling above the boiling range of the desired product; cooling said overhead from the primary fractional distillation, separating gas rich in hydrogen and containing some hydrogen sulfide from a liquid fraction containing the desired motor fuel components, dissolved hydrogen sulfide and low boiling hydrocarbons; subjecting said liquid fraction to a fractional distillation at a substantially lower pressure than said primary fractionation pressure to separate hydrogen sulde and low boiling hydrocarbons from the desired motor fuel components; subjecting said residue fraction from the primary fractional distillation to a further fractional distillation at a pressure substantially lower than the pressure of the primary fractional distillation to separate as distillate a relatively small amount of a motor fuel fraction boiling within the distillation range of the desired product from the heavy components boiling above the distillation range of the desired product; and blending said distillate with said desired motor fuel fraction.

9. A process for the production of a motor fuel of reduced gum content which comprises contacting a hydrocarbon fraction component boiling in the motor fuel range with a sulfur resistant hydrogenation catalyst in the presence of a hydrogen containing gas at a pressure above about 200 p.s.i.g. and a temperature to minimize cracking, passing the hydrogenation product together with unreacted hydrogen to a primary fractional distillation maintained at substantially the pressure of the hydrogenation zone, removing hydrogen, normally gaseous hydrocarbons and at least a major proportion of the fraction boiling in the motor fuel range as distillation overhead from a residual fraction containing heavy components boiling above the motor fuel range, cooling the overhead from the primary fractional distillation zone to effect partial condensation thereof, separating a gas containing hydrogen from the cooled-overhead and subjecting the condensed portion of the cooled overhead to a secondary fractional distillation at a pressure substantially below that of the primary fractional distillation and recovering from said secondary fractional distillation a motor fuel of reduced gum content.

l0. The process of claim 9 in which the residual fraction containing heavy components boiling above the motor fuel range is subjected to a further fractional distillation at a pressure substantially lower than the pressure of the primaryfractinaldisti11ationi to separate as distillate-aA fraction boiling-Within the motor fuelr'mge andlblendin'gl said -lastmentiqnedl fractiony with' the? motor fue'l ofl reducedgum content;

11. The process of claim 9 in which thebsuhur` resistant hydrogenation catalyst is a molybdenum-oxidealurnua dehydro-aromatization catalyst which has become spent for dehydro-aromatization purposes.-

12. The process of claim 11 in whichthe surface area of the spent dehydro-aromatization catalyst? isV about 55 square meters per gram.v

References Citedimvthee'ileof ths patent UNITEDsTATEs PATENTS Boydaetr-h'al. :.....g Aug. 26, 1941 P enisten. Aug. y25, 1942 Hays Y Sept. 21, 1943 BuddrusY et al. Oct. 24, 1944 Home et al. Aug, 1, 1950 Strang Sept. 11, 1951 Cornell Oct. 14, 1952 Porterl et 611.v Oct. 20, 1953 De Rosset et al. Mar. 9, 1954 Porter et a1 Aug. 10, 1954 Porter Dec. 21, 1954 Engel etial'. Dec. 21, 1954 Porterfetzal. Nov. 6,V 1956 De Rosset July 16, 1957 

1. A METHOD OF REFINING A SULFUR-CONTAINING HYDROCARBON MOTOR FUEL FRACTION WHICH COMPRISES HYDROGENATING SAID FRACTION WITH A HYDROGEN-CONTAINING GAS AT A PRESSURE ABOVE 200 P.S.I.G. UNDER CONDITIONS WHEREIN AT LEAST A PORTION OF THE SULFUR IS CONVERTED TO HYDROGEN SULFIDE, SUBJECTING THE HYDROGENATION PRODUCT TO A PRIMARY FRACTIONAL DISTILLATION AT SUBSTANTIALLY THE PRESSURE OF THE HYDROGENATION ZONE AND IN THE PRESENCE OF UNREACTED HYDROGEN-CONTAINING GAS SUPPLIED TO SAID HYDROGENATION ZONE TO EFFECT A SEPARATION BETWEEN A FRACTION CONTAINING DESIRED MOTOR FUEL COMPONENTS AND A FRACTION CONTAINING UNDESIRABLE HIGH BOILING COMPONENTS, SEPARATING HYDROGEN-CONTAINING GAS FROM SAID FRACTION CONTAINING MOTOR FUEL COMPONENTS, AND DISTILLING SAID MOTOR FUEL FRACTION AT LOWER PRESSURE TO REMOVE COMPONENTS LOWER BOILING THAN THE DESIRED MOTOR FUEL COMPONENTS. 